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Problem with disassembler and SIGILL signal

  • Hi there ,

    I'm coming here for some help since I saw that my programm is stopping in the middle of it's execution .
    Then I saw a SIGILL error just when I start my application .

    I was thinking that I could find where my problem is but I can't because it's openning the disassembler only and not my cpp or header file.

    How can I translate the disassembler language to find where is my corruption error ?

    thanks by advance.

    BTW I'm in debug mode.

  • Lifetime Qt Champion

    HI and welcome
    Did you compile the app as debug?

  • Yes i'm in debug mode

  • Lifetime Qt Champion

    So app should be compiled in debug mode and hence have debug information?
    You are seeing assembly as source is not there.
    That is often due to debugging a released version.

    To verify your debugger is working set a break point in your source and see it stop.

  • well when I'm using abreak point in my main.cpp I see my app stopping when clicking on the play buton with the bug ( i'm on QT creator). I also see that my app is in debug and not in release mode.

  • Lifetime Qt Champion


    And in this case the/your code is shown ?

  • Yes it's popping on the break point and not showing me the disassembler again.

  • Lifetime Qt Champion


    So it sounds like where ever it crashes its not in
    your code and it shows assem as it have no source ?

  • I don't know it sound like this yes , but it crashes at the starting point of my app, just showing my first window and then crashing.
    But when I just run my app it's starting normally and then crashing after a couple of minutes without any explications .
    That's why I need to debug, but if the problem is something out of the app I don't know how to deal with it.

  • Lifetime Qt Champion

    Dont you have idea in where in the app it could be ?
    Or what action or processing that is going on when crashing.

    When it crash, did the call stack showed more info on where it was?
    "Viewing Call Stack Trace"

  • Alright after setting a break point as you recommended I was using F10 to check if there's some code that was walling the SIGILL signal , I think I found where my problem is .

    That's my main :

    int main(int argc, char *argv[])
        QApplication a(argc, argv);
        QTranslator qtTranslator;
                   "qt_" + QLocale::system().name(),
        MainWindow w;;
        return a.exec();

    All of this is running nice except when I'm trying to run (with F11 or f10 key ) the return a.exec() which giving the SIGILL signal

    Ps : I set the breakpoint first on and then on the line bfore the return function.

  • Lifetime Qt Champion

    I dont like the look of
    Since you give it address of a local variable.
    So if it thinks it owns the translator ( as expects a pointer) then it will be double deleted by
    "a" and by running out of scope. (after .exe())

    Could you try to new it and see if it still crashes?

    Hmm Docs dont say it owns it.

  • I have to say that I found this piece of code and just add it to my program since I had some pop-ups written in english ( I'm french).

    So is something like this that you mean by new it ? :

    QTranslator *qtTranslator = new QTranslator;
                  "qt_" + QLocale::system().name(),
       return a.exec();

    because I can't even copile like this ...

  • Lifetime Qt Champion

    except now its pointer, u must get rid of &

  • That's compiling but when I'm debugging it's still crashing at the same point ...

  • Moderators

    SIGILL is very unusual, it often means the binary is corrupt (it's the illegal instruction signal). What compiler are you using?
    As for @mrjj's suggestion, you can still create on the stack, but do unregister the translator before returning from main(), e.g.:

    int main()
        // ...
        QTranslator qtTranslator;
        qtTranslator.load("qt_" + QLocale::system().name(), QLibraryInfo::location(QLibraryInfo::TranslationsPath));
        int retcode = a.exec();
        return retcode;

  • I am using Gdb as debugger and Gcc as a compiler , I forget to precise that I was on a raspberry Pi 3.
    I would try your way and come back again.

  • Lifetime Qt Champion

    Ok. it was not the translator it seems.

    Do you have global object or anything else that might run out of scope and be deleted twice?
    You should try putting break point in mainwindow destructor and see if it gets to that part.

  • I have a .h and .cpp named global Where I put 2 global variables as extern. Maybe it's the problem I'm Setting a point break on the Main window and sending you my global.h and global .cpp


    #ifndef GLOBAL_H
    #define GLOBAL_H
    #include <QString>
    class QString;
    extern QString OnlinePath;
    extern int Var;
    #endif // GLOBAL_H


    `#include "global.h"
    #include <QString>
    QString OnlinePath= "";
    int Var = 0;

  • Moderators

    Are you sure that this compiler produces binaries for that particular instruction set? Look up the compatibility of your gcc version with the instruction set of that particular Pi.

  • Lifetime Qt Champion

    Hmm dont seems like it as just a Qstring.
    Its more if you have a widget and assign parent.
    Then both scope and parent might delete it and it might crash.

    Dont the call stack give hint what it was doing ?

  • @kshegunov Sorry I didn't understand anything I'm not really used with the debuggers.

    @mrjj Hum I am associating widgets to a parent when using a QStackWidget for example I got my main window with some widgets in it. It the main ui of my application.

    I am adding some widgets in a QStackedWidget on the MainWindow and calling them by using their names .


    MainWindow::MainWindow(QWidget *parent) :
        ui(new Ui::MainWindow)
        AccueilWindow = new Accueil(this,"AccueilWindow");
    void MainWindow::changeOnglet(QString name)
        if ((name == AccueilWindow->objectName())&&AccueilWindow)
        else if ((name == AlarmesWindow->objectName())&&AlarmesWindow)


        Ui::MainWindow *ui;
        Accueil *AccueilWindow;
        Alarmes *AlarmesWindow;

    The alarm.cpp

    Alarmes::Alarmes(QWidget *parent,QString AlarmesWindow) :
        Alrm_ui(new Ui::Alarmes)
        connect(this,SIGNAL(changeInterface(QString)),qobject_cast<MainWindow *>(parent),SLOT(changeOnglet(QString)));


    namespace Ui {
    class Alarmes;
    class Alarmes : public QWidget
        explicit Alarmes(QWidget *parent ,QString AlarmesWindow);
        virtual ~Alarmes();

  • Lifetime Qt Champion

    Nothing springs to eye. Seems you let the Qt system handle it.

    If you create a default Widgets project and run it on the pi.

    Does that also crash at close?

  • If i delete the whole Qtranslator thing it seems that's not ceashing anymore , there just a message saying starting the debug and debug ended. I assume that's ok ...

    I didn't tried to let some other programm running to see if there's something but I didn't found any problems on an other application .

    Edit : It seems that other programs have no problem ..

    And I don't have any more troubles if my main.cpp is like :

    int main(int argc, char *argv[])
        QApplication a(argc, argv);
    //    QTranslator qtTranslator;
    //        qtTranslator.load("qt_" + QLocale::system().name(), QLibraryInfo::location(QLibraryInfo::TranslationsPath));
    //        a.installTranslator(&qtTranslator);
        MainWindow w;;
    //    a.removeTranslator(&qtTranslator);
        return a.exec();

  • Lifetime Qt Champion

    Im not sure what to conclude from that :)
    But seems to be related to it anyway then.

  • Yes I'm really not sure about it that's really pointing on this but don't know what's wrong ...

    I think I'm going to create some buttons that are written in my language instead of using the Qt popup default buttons.

    Thanks for help I'm closing this subject and put it as solved .

    See you in a close future I think ^^

    Edit Seems to be the return a.exec() that is bugged don't know why ^^

  • Lifetime Qt Champion

    @Amaury said in Problem with disassembler and SIGILL signal:

    Edit Seems to be the return a.exec() that is bugged don't know why ^^

    For QApplication it has setting that says When last window closed,
    exit the event loop ( exec() ) and die.
    This is in effect sort of the same as
    app.connect(&app, SIGNAL(lastWindowClosed()), &app, SLOT(quit()));

    So if some sort of instruction that gets called when deconstructing then it will
    show exec() as the the point of crash.

  • Lifetime Qt Champion


    Out of curiosity, why are you removing the translator before starting the event loop ? Doing it like that raises the following question: why set a translator in the first place ?

  • @SGaist I am removing the translator because it looked like that was this function that send the SIGILL signal .
    After all it seems that it doesn't changed anything, but I do need it , just that I can translate my pop-ups in a different way.

    @mrjj I'm going to look those potential solutions and post here if I get the answer.

  • Moderators

    It'd be helpful if you also extract the assembly (a few lines) from the point of the crash, where you get the SIGILL.

  • Those are the first 15 lines of the disassembler where I get my Sigill signal : it happens on line 6

    0x6f6a2dd4                   00 00 00 00  andeq	r0, r0, r0
    0x6f6a2dd8                   00 00 00 00  andeq	r0, r0, r0
    0x6f6a2ddc                   00 00 00 00  andeq	r0, r0, r0
    0x6f6a2de0                   fe e1 6e f2  vorr	q15, q15, q15
    0x6f6a2de4                   1e ff 2f e1  bx	lr
    0x6f6a2de8                   1d 0f 19 ee  mrc	15, 0, r0, cr9, cr13, {0}
    0x6f6a2dec                   1e ff 2f e1  bx	lr
    0x6f6a2df0                   9f 2f 90 e1  ldrex	r2, [r0]
    0x6f6a2df4                   01 30 82 e0  add	r3, r2, r1
    0x6f6a2df8                   93 2f 80 e1  strex	r2, r3, [r0]
    0x6f6a2dfc                   00 00 52 e3  cmp	r2, #0
    0x6f6a2e00                   fa ff ff 1a  bne	0x6f6a2df0
    0x6f6a2e04                   03 00 a0 e1  mov	r0, r3
    0x6f6a2e08                   1e ff 2f e1  bx	lr
            Function: OPENSSL_cleanse

  • Hi there ,

    after a day of research I finnaly didn't found what's the real problem .

    I read that the return a.exec() Will execute only when a signal is send to it ( when nothing is shown).

    I maybe found a track that leads to my destructors , I have some sql request and QUrl posts in my program , ido I need to delete them in the destructor , would that cause a problem if the program is executed during a long time ?

    Everything is compiling fine and my program is running well but after a period of time it's crashing.

    Finally I was thinking about the SIGILL signal ,when I F10 or F11 on this it's running this part of the program but if it's closing everything on the app would it be normal to have this signal ?

    don't know if I was clear ...

  • Lifetime Qt Champion

    SIGILL is not normal.
    From normal program errors you do not get this in any easy way.
    So the big question is. Can you can get SIGILL from a normal GUI program or
    only when using your full code?

    It might be some sort of corruption but impossible to guess at :)

  • I didn't tried that but it works with another program I don't have any SIGILL error ...

    the problem with this is that I have something like 18 pages and 500 lines by pages on average.

    So that said to find out where the problem is do I have to check each lines of my program ? :/

  • Lifetime Qt Champion

    Well if ONLY this program does it. Its not compiler.
    But you should be really clear about it.
    Else you can waste tons of time.

    So yes, if it is program error in your code. You will need to find the actual line/the bug.

    You can try but its takes time to use and understand.

  • Thanks for the support , I need to debug my program before I continue so I prefer to waste little time to understand and use the program.
    I can't try to debug the code line per line it would take too long and it should be everywhere .

    At least when I'm done with it I finally have to find a solution to start my app on boot but for now if it crashes all the time it's not really usefull.

  • Lifetime Qt Champion

    Well u should look for array copy. dangling pointers.
    old char * types and stuff like that.
    To get SIGILL from program bug , you must corrupt
    something in the code segment.
    Easy way is to use dangling pointer.

    So maybe you can guess at functions where it might happen.

  • @mrjj
    Well right now you're talking to me in japanese ^^
    I'm going to have a look on that didn't had time yesterday , I think I can be helped for one thing or two :)
    I'll come back if my problem is solve or not.

  • Lifetime Qt Champion


    Oh :) sorry.
    What i mean is SIGILL means "what the hell is that instruction" from the cpu.
    This can happen if compiler setting is slightly off for target.
    you can also have it happen if you write over the end of an array
    or use a pointer that is not set.
    MyClass *c1; /// dangling pointer
    Then when CPU tries to run the func it sees some random garbage at that location
    and might say SIGILL.

  • Alright that's clearer ^^
    So if I need to create a dangling pointer where do I need to declare it ?
    into the class itself ?

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